A great variety of floodlights have been disclosed and used in the prior art. Among these are many with lenses or other refractive structures over their light sources to aim the light being emitted, and many others using reflectors behind their light sources for the same purpose. This invention deals with floodlights of the latter type.
Such floodlights include a light source and one or more reflector surfaces with a case. These floodlights have a light-emitting opening, which is often planar and which may be covered by a light-transmissive cover, preferably a transparent cover made of glass or the like.
In recent years, substantial efforts have been directed toward development of reflector-type floodlights which direct emitted light in a predetermined off-center direction, that is, in a direction which is not normal (perpendicular) to the light-emitting opening plane, in order to satisfy certain types of lighting requirements. One such type of reflector floodlight is referred to as a "cut-off" floodlight because the area which it is intended to iluminate is well defined. If floodlights have well-defined areas of illumination, a number of them can be arranged for more efficient use of power in lighting large areas.
To best describe some of the deficiencies and problems with cut-off floodlights of the prior art, it will be helpful first to describe briefly a typical cut-off floodlight. The cut-off floodlight has a light-emitting opening plane which is generally on the lower side of the floodlight housing when it is in use. Light is directed downwardly, of course, and by virtue of reflectors within the housing is directed at least to some extent toward one side--often referred to as the front. The front edge of the emitted light has a cut-off location, beyond which it is desirable to have as little light emitted as possible.
Such cut-off reflector-type floodlights of the prior art often have had substantial glare and spill light beyond their cut-off points (lines). As a result, such floodlights are less efficient in operation than desirable.
A very significant problem with such cut-off floodlights is that their main beam directions are quite close to the aforementioned normal (perpendicular) direction. That is, the main beam direction is not angled enough in the forward direction. As a result, too much light intensity is concentrated on positions immediately below or close to immediately below the light, and the illuminated areas approaching the forward cut-off point are insufficiently lit.
It is very typical with such cut-off floodlights that the main beam direction is about 20 degrees in front of the normal (perpendicular) direction, while the cut-off angle may be on the order of 80 degrees from perpendicular (when the light-emitting opening plane is horizontal). This provides inadequate evenness of light distribution over the area to be illuminated.
Because of such deficiencies in cut-off reflector floodlights of the prior art, it is often necessary to mount the floodlights with their light-emitting openings tilted toward the forward direction. Such tilting, of course, shines more light toward the forward direction. But tilting also moves the cut-off point so that light is being wasted. This represents an inefficient use of light. And, it is important to note that the tilting of such floodlights increases the possibility of water ingress, with all the attendant disadvantages.
In cut-off reflector-type floodlights, it is desirable that the main beam direction be directed more toward the front without the need to tilt the lamp such that the light-emitting opening is away from a horizontal orientation. Stated differently, it is highly desirable for the angle of the main beam direction to be much closer to the cut-off angle, so that the entire area is lit more evenly and efficiently.
As previously suggested, it is desirable to have a more distinct front cut-off to minimize spill light and glare beyond the cut-off. And, it is desirable to reduce concern about water ingress by providing a floodlight which can be used more often with the light-emitting opening in a horizontal orientation.